1. Field of the Invention
The present invention relates to concrete plants and, more particularly, to concrete recycling systems for concrete plants. 2. Description of the Related Art
One conventional concrete recycling effort is to reclaim cement slurry. See, e.g., U.S. Pat. No. 4,226,542, which is incorporated herein by reference. More particularly, cement slurry reclamation techniques for concrete plants separate aggregate and coarse sand constituents from returned concrete mix and the remaining ingredients are stored in slurry form for possible consumption during a subsequent production day. Typically, returned concrete mix is dumped into an inlet hopper having a screw classifier for removing aggregate and coarse sand, and a weired channel enabling gravity flow of the water, cement fines and sand fines constituents into a slurry vessel. A motor agitates the slurry within the slurry vessel to prevent setting. Typically, the motor runs constantly while there is slurry in the slurry vessel. Unfortunately, conventional concrete recycling has various limitations or constraints that lead to inefficient recycling. The inefficiencies pertain, for example, to high energy consumption and unusable slurry or slurry water.
Thus, there is a need for improved approaches to perform concrete recycling.
Broadly speaking, the invention relates to an improved concrete plant design with robust recycling capabilities and high energy efficiency. The invention can be implemented in numerous ways and configurations. Several embodiments of the invention are discussed below.
According to one embodiment of the invention, a concrete recycling system includes at least: a slurry vessel that receives slurry provided from concrete being returned, the slurry vessel having an agitation device; a motor that drives the agitation device; and a control system that controls at least one of duration and frequency with which the motor drives the agitation device.
According to another embodiment of the invention, a method for recycling concrete includes at least the operations of: removing at least a portion of aggregates from the concrete, thereby leaving at least slurry; storing the slurry in a slurry vessel, the slurry vessel having an agitation element driven by a motor; and agitating the slurry within the slurry vessel by driving the agitation element with the motor such that the energy used in performing the agitation is varied based on the load on the motor.
According to still another embodiment of the invention, a method for controlling a motor for agitating a cement slurry includes the operations of: activating the motor to agitate the cement slurry; monitoring a load on the motor during the activating; determining a suitable agitation duration based on the load; and deactivating the motor so as cease agitating the cement slurry after the suitable agitation duration has passed since the activating was initiated.
According to yet still another embodiment of the invention, a method for controlling a motor for agitating a cement slurry includes the operations of: monitoring density of the slurry density; determining a suitable agitation duration based on the density; and periodically activating the motor for the suitable agitation duration.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.